The present invention relates to a method and means for dispensing a fluid within a pipe or conduit and more particularly for dispensing a lubricant for facilitating cable pulling and installation of electrical cables in an extended conduit.
Electrical wiring of buildings, and more particularly of commercial and industrial buildings, is generally effected by installing a plurality of conduits under the floors or above the ceilings and through the walls from end to end of the buildings, between an electrical inlet station and a plurality of distribution outlets and connection boxes. Electrical cables are installed in the empty conduits by first placing a flexible pull strand, or fishtape, by pushing it through a given length of conduit, from a connection box to another, or from one end of the conduit to the other. The electrical cables to be pulled through the conduit are attached to an end of the fishtape, and the other end of the fishtape is manually, or mechanically, pulled such as to pull the electrical cables from one end of the conduit to the other.
In installations where the conduit is relatively long, or where there are bends in the conduit, lubricant is applied to the surface of the electrical cables as they enter the conduit, in order to reduce as much as possible the friction between the electrical cable peripheral surface and the inner surface of the conduit wall. While one man pulls on the fishtape at one end of the conduit, another man smears a paste lubricant on the electrical cables entering the conduit at the other end or, in the alternative, wipes the electrical cables with a rag impregnated with lubricant, or squirts lubricant on the cables. The electrical cables are very slippery, which prevents the man at the inlet of the conduit from helping by pushing the cables into the conduit, and the lubricated cables being inserted in the conduit accumulate dirt and grit from anything they touch. Furthermore, most of the lubricant coating the electrical cables is transferred to the conduit wall proximate to the inlet of the conduit, and very little lubricant remains on the surface of the cables where it is most needed at bends and further down the conduit.
Diverse attempts have been made in the past to overcome the inconveniences of manually lubricating electric cables prior to pulling through a conduit. For example, U.S. Pat. Nos. 3,605,251 and 3,605,947 disclose permanently installing rupturable containers of lubricant in an electrical conduit, at predetermined locations along a run of conduit. The containers are broken during installation of electrical cables, thus releasing the lubricant and reducing the friction between the cables and the conduit wall during pulling of the cables through the conduit. The inconveniences of such an arrangement are many, as it requires modifications of conventional electrical conduits, lubricant is available only when electrical cables are first installed through a conduit, and manual lubrication must be resorted to when additional cables are passed through the conduit at some later date.
U.S. Pat. No. 3,858,687 discloses low profile flexible rupturable lubricant containers attached at appropriate locations along an electrical cable being pulled through a conduit. The containers are ruptured by pressure when the cable is pulled through zones of heavy friction between the cable and the conduit wall, thus releasing the lubricant. Such a lubricating system is complicated, and there is no assurance that lubricant will be provided where most needed, or that not all the lubricant will be exhausted prior to finishing pulling an electrical cable through a conduit.
U.S. Pat. No. 3,908,799 discloses an apparatus and method for pre-lubricating a conduit interior prior to inserting electrical cables therethrough. The lubricant is contained in tubing sections interconnected by rods. The tubing sections are provided with an aperture through which lubricant is dispensed by progressively squeezing the tubing sections by means of clamping loops forming parts of the rods and by relatively displacing the tubing sections and the clamping loops. Such an arrangement requires that the conduit be empty so as to afford passage through the conduit for the tubing sections containing the lubricant and the accompanying rods. Application of lubricant through the conduit is somewhat haphazard and difficult to be effected.
U.S. Pat. No. 3,438,461 discloses a collapsible bag filled with lubricant which is attached between a fishtape and the end of the electrical cables being pulled through a conduit. The collapsible bag is filled with lubricant and is contained in a flexible sleeve, which is caused to extend as a function of the tension exerted on the fishtape so as to contract the sleeve peripherally and expel lubricant from the collapsible bag. Such an arrangement also presents the inconvenience of applying lubricant in a haphazard manner, and the lubricant applicator may be completely emptied right at the beginning of a run, such that very little lubricant, if any, is applied to the conduit walls towards the end of the run.
The disadvantages of the prior art are remedied by the present invention which provides a method and means for evenly applying lubricant all along the length of a conduit, which requires very little lubricant, which coats the conduit wall with lubricant where it is most needed, which does not leave an excess of lubricant in the conduit, which permits to lubricate electric cables, and the like, only after they have been introduced in the conduit, and then only as a result of engagement with the surface of the conduit wall, which is in the form of a sealed cartridge having its own supply of lubricant and therefore avoiding contamination of lubricant remaining in an opened container, which, in addition to lubricating the wall of the conduit simultaneously with the installation of electrical cables therein, also cleans the wall free of dirt, and which provides a smooth low friction bearing remaining at the inlet of the conduit which prevents damaging contact between the electrical cable periphery and the sharp edge of the conduit end.